Foundation issue: rat tunnels under the footing

[seamlyne]

We recently dealt with rats in our basement, and found some damage they'd created with their tunneling. The house has two foundations on the West and North sides and in the '50s the space between them was partially dug out to make room for plumbing. The dirt on the exterior was never shored up and when the rats started digging they collapsed a few feet of the dirt "wall" (first attachment).

I can build a wall to shore up the dirt (second attachment), but there is a void under the exterior foundation footing that I'm not sure how to effectively fill in the process.

Because our family economy is as screwed up as the national economy it's got to be DIY.

The void is only a few feet wide, and doesn't extend all the out, i.e. we can't see daylight under the foundation (yet). That area of the foundation is sheltered by a deck with a ceiling underneath the joists to keep the area dry (and direct rain to the roses).

Any advice how to proceed? Do I make mud and pack it in there as I'm building the shoring wall? Do I rent some sort of pump and pump it in?

[pushkins]

How wide is that overhang from one cinder block wall to the other ?
You could build your new "retaining wall" and once you get to the top course (above the bottom of the foundation of the exterior wall) first compact existing soils as much as you can then use sand and water to settle fill the void. Fill the void with sand, NOT DIRT, then add water to make it soupy you then need to tamp it all to get the water to settle the sand, just like playing in the sand at the beach, you might have to do this a couple of times eventually your sand will end up higher then the footing. Do this from the exterior side once you have the support wall built (higher than the existing wall) dig a small hole into the void and do as mentioned above
Then either leave or cap it off like in your picture.

[seamlyne]

Thank you! I was beginning to wonder if there was an answer out there.

How wide is that overhang from one cinder block wall to the other ?

The "tunnel", as we've called it since I was a kid, is 3-1/2', maybe 4' wide. Wide enough that if I put my back against the interior foundation, I can't touch the other side, but not so wide that standing in the center I can't touch both with my fingertips. I'm average height and have to crouch to avoid smacking my head on the floor joists above.

your sand will end up higher then the footing. Do this from the exterior side once you have the support wall built (higher than the existing wall) dig a small hole into the void and do as mentioned above
Then either leave or cap it off like in your picture.

SAND. Hadn't thought of that, but it makes perfect sense. As in your explanation, I plan to use the collapsed dirt to back-fill as I build the support wall until there's not enough space to do that - it's pretty fine and dry, so would I use water there too? Or just leave it dry?

[pushkins]

Make the backfill slightly wet and compact it down in 6" sections, in other words fill in 6" of dirt compact it down by tamping as hard as you can, then add another 6" and tamp down etc...etc... add a small shower of water over each backfill before tamping.
You could opt out of using the natural dirt all together and just use sand but you'd probably need a fair pile.
Sand is a perfect sub base, it doesn't expand or contract, water has little effect on it (unless it starts to flow). It's very often used in engineering issues just like yours.

[seamlyne]

Make the backfill slightly wet and compact it down in 6" sections, in other words fill in 6" of dirt compact it down by tamping as hard as you can, then add another 6" and tamp down etc...etc... add a small shower of water over each backfill before tamping.
You could opt out of using the natural dirt all together and just use sand but you'd probably need a fair pile.
Sand is a perfect sub base, it doesn't expand or contract, water has little effect on it (unless it starts to flow). It's very often used in engineering issues just like yours.

Awesome, thanks again!